Monday, March 21, 2005

Data on remittances sent by South African migrant workers to their rural households of origin allow an explicit test, to our knowledge the first of its kind for humans. Using estimates of the fitness benefits and costs associated with the remittance, the genetic relatedness of the migrant to the beneficiaries of the transfer, and their age- and sex-specific reproductive values, we estimate the level of remittance that maximizes the migrant worker's inclusive fitness. This is a much better predictor of observed remittances than is average relatedness, even when we take account (by means of a multiple regression) of covarying influences on the level of remittance. But the effect is modest: less than a third of the observed level of remittances can be explained by our kin-altruism model.

We've discussed inclusive fitness and kin selection before. This is a test of kin selection in humans, and shows that evolutionary hypotheses can generate accurate predictions about humans, too.